Process for finishing cotton with carbamate crosslinking agents formed in situ in the fibers

ABSTRACT

Cotton fabrics are impregnated with aqueous formaldehyde-methyl carbamate mixtures at molar ratios of about 2:1 to 4:1 respectively, and a pH of about 10, then heated in a package without evaporation to yield dimethylol methyl carbamate in situ in the fibers. Alternatively, the package, could be held for 16 hours at room temperature. The adduct is produced in yield equivalent to 2.5 to 10% dimethylol methyl carbamate. The wet impregnated fabric is removed from the package, dried, then acidified, and catalyst is applied. It is cured to yield a crosslinked fabric having durable press properties.

United States Patent Inventors Norton A. Cshen Metalrie; Robert M. Reinhardt, New Orleans; John 1). Reid, New Orleans, all of La.

Appl. No. 844,166

Filed July 23, 1969 Patented Sept. 21, 1971 Assignee The United States 01 America as represented by the Secretary of Agriculture PROCESS FOR FINISHING COTTON WITH CARBAMATE CROSSLINKING AGENTS FORMED IN SITU IN THE FIBERS 3 Claims, No Drawings US. Cl. 8/ 116.3, 1 17/ 1 39.4 Int. Cl 006m 13/14, D06m 13/40 FieldotSearch 8/ll6.3

[56] References Cited UNITED STATES PATENTS 3,420,696 6/ l 969 Cotton et al. 8/1 163 OTHER REFERENCES Mehta et al., Journal of the Textile Institute Vol. 58, pp. 279- 292 (1967) Cashen et al., Textile Research Journal, Vol. 39, No. 4, pp. 381- 383 1969) Primary Examiner-George F. Lesmes Assistant Examiner-J. Cannon Attomeys-R. Hoffman and W. Bier ABSTRACT: Cotton fabrics are impregnated with aqueous PROCESS FOR FINISHING COTTON WITH CARBAMATE CROSSLINKING AGENTS FORMED IN SITU IN THE FIBERS A nonexclusive, irrevocable, royalty-free license in the invention herein described throughout the world for all purposes of the U.S. Government, with the power to grant sublicenses for such purposes, is hereby granted to the Go ernment of the United States of America.

This invention relates to formation of aldehyde-carbamate products. Specifically this invention relates to the formation of these adducts, monomethylol and dimethylol carbamates, in situ within the structure of the cotton fiber. More specifically, this invention relates to the reaction of formaldehyde with alkyl carbarnates to produce cross-linking adducts under alkaline conditions within the structure of the cotton or other cellulosic fiber. The adducts thus produced can be used to cross-link cellulosic textiles and other materials under acid conditions, to produce chemically modified textiles and other products. the textiles having improved dry and wet wrinkle resistance and crease-setting properties when in the fabric form.

The primary object of the present invention is to provide a method of producing wrinkle resistant, durable press cotton textiles having all the advantages associated with low resin add-on,

Another object of the present invention is to provide a process wherein the primary object is served and supplemented by decreased expended chemicals.

A third object of the present invention is to provide a process wherein the primary and other objects are served while also providing fabrics with desirable physical properties, such as enhanced hand, increased comfort, etc. A prior art process is known for producing an aldehyde-carbamate condensation product in situ within cotton fibers. Belgian Pat. No. 664,757 discloses a process wherein cotton fibers were treated with an aqueous mixture of aldehyde, carbamate. and a latent acid catalyst at elevated temperatures to impart dimensional stability to linen borders. Those skilled in the art have found that when the aldehyde used is formaldehyde the conditions cited (acid) are conductive primarily to monomethylolation of the carbamate and reaction of this intermediate to give a singly linked substituent, along with methylenic cross-linking of the cellulose.

In contrast to the prior art process the instant invention relates to a process for the dimethylalation of the carbamate under alkaline conditions (equation I below), with a subsequent reaction with cotton cellulose under acid conditions to give a cross-link containing the alkyl carbamate moiety (equation [I below).

The equation pertinent to the instant invention are:

O CHzOH H II (I) CHgOCNHz-HHCHO CHaOCN CHzOH Methyl Formal Dimethylol methyl carbamate dehyde carbamate (DMMC) H (11) HO CHzIiICHzOH+2Cell-OH (DMMC) (911111068 Cell-OCHzNCHzOCelH-2Hz0 Crossllnked cellulose An added feature of the instant invention is that the process lends itself to preferential cross-linking of cellulose. A onesided finish can be produced by the process of the instant in vention as well as a more conventional finish that is uniform throughout the structure of the cotton or other cellulosic fabric.

The process of the instant invention can be described thusly. A cotton or other cellulosic textile is impregnated with an aqueous mixture of formaldehyde and methyl carbamate in molar ratios of about 2:1 to 4:1, respectively, preferring the latter. The mixtures are generally applied to fabrics at a pH of about 10. The concentrations generally observed are equivalent to about from 2.5 percent to 10 percent dimethylol methyl carbamate. The wet impregnated fabric is placed in an airtight package and heated for about 30 minutes at 60 C., or alternately, the impregnated fabric can be held (without evaporation) at room temperature for about 16 hours, then removed from the container and dried. The dried fabric is then catalyzed, preferably by fogging with an acidified 5 percent solution of either magnesium chloride or a mixture of magnesium chloride and citric acid (pH about 2.5 The fabric with the in situ prepared dimethylol methyl carbamate and catalyst is then cured for about from 3 to 5 minutes at about 160C. to yield a cross-linked fabric with excellent durable press properties.

Deviating from the norms of the instant invention the results can give unsatisfactory products. For example, if the molar ratio of formaldehyde to methyl carbamate is decreased from 4:1 to 2:1 the carbamate adduct produced in situ is a mixture of monomethylol and dimethylol carbamates. The presence of a considerable concentration of monomethylol methyl carbamate can result in a finish which does not have a high level of resistance to damage by retained chlorine upon bleaching during laundering. These and other factors are explained in detail in a paper by these inventors bearing the title Cross-linking Cotton Fabric with Methylolated Carbamate Agents Formed In situ, which appears in Textile Research Journal 39,381-383 (1969).

The invention is illustrated in the examples.

To summarize, the instant invention can best be described as an efficient process for imparting durable press properties to cotton and other cellulosic fabrics by treating the fabric with a solution, adjusted to a pH of about 10, of formaldehyde and methyl carbamate in quantities corresponding to mole ratios respectively of about 2:1 to 4:1 to yield a dimethylol methyl carbamate adduct formed in situ in the fibers, which adduct cross-links with said cotton and other cellulosic fabrics upon heat treating in the presence of an acid type catalyst to render the finished textile wrinkle resistant.

EXAMPLE 1 A swatch of 3.2 oz./sq.yd. cotton printcloth (desized, scoured, and bleached) was padded to percent wet pickup with an aqueous solution containing 5.55 percent methyl carbamate, a concentration equivalent to the amount of carbamate in 10 percent dimethylol methyl carbamate, in the presence of an amount of formaldehyde required to give a molar ration of 4:1 formaldehyde carbamate. After 30 minutes oven heating at 60C. in a sealed polyethylene bag, the fabric was removed and dried at the same temperature for 3 minutes. A 5 percent solution of magnesium chloride, pH 2.5, was applied with a nebulizer, then fabric was cured for 3 minutes at C.

EXAMPLE 2 A second swatch of 3.2 oz./sq. yd. cotton printcloth (desized, scoured, and bleached) was treated as in example 1 with the following exception: the pad bath contained 2.75 percent methyl carbamate, a concentration equivalent of the amount of carbamate in 5 percent dimethylol methyl carbamate, with formaldehyde required to give a molar ratio of 4:1 formaldehyde/carbamate.

EXAMPLE 3 A third swatch of 3.2 oz./sq. yd. cotton printcloth (desized, scoured, and bleached) was treated as in example 1 with the following exception: the pad bath contained 1.37 percent methyl carbamate, a concentration equivalent to the amount of carbarnate in 2.5 percent dimethylol methyl carbarnate, with formaldehyde to give a molar ration of 4:1 fonnaldehyde/carbamate.

EXAMPLE 4 A fourth swatch of 3.2 oz./sq. yd. cotton printcloth (desized, scoured, and bleached) was treated as in example 1 with the following exception: the pad bath contained 5.55 percent methyl carbamate, a concentration equivalent to the amount of carbamate, in i percent dirnethylol methyl carbamate, in the presence of an amount of formaldehyde required to give a molar-ratio of 2: l formaldehyde/carbamate.

EXAMPLE The following chemical and physical properties were obtained using procedures as in examples 1, 2, 3, 4.

Cotton printcloth, 3.2 oz./sq. yd. was padded with an aqueous solution adjusted to pH 10, containing formfldehyde and methyl carbamate (molar ratio 4: 1) equivalent in the concentration to a 19 percent solution of dimethylol methyl carbamate. The wet fabric was rolled onto a glass tube, wrapped with polyethylene, and allowed to stand at room temperature (23.3 C.) for l6 hours. The fabric was then dried at 60 C. for 3 minutes, sprayed with a solution of 5 percent MgCl 6H O which had been adjusted to pH 2.5, and cured at 160 C. for 5 minutes. The treated fabric had 0.50 percent bound nitrogen, and a dry and wet wrinkle recovery value'of 276 and 274(W +F) respectively.

EXAMPLE 7 Cotton twill, 7.0 oz. lsq. yd. Type 413, was padded to approximately percent wet pickup with an aqueous solution adjusted to pH 10, containing formaldehyde and methyl carbamate (molar ratio 4:1) equivalent in the concentration of a 10 percent solution of dimethylol methyl carbamate. After 30 minutes oven heating at 60 C. in a sealed polyethylene bag, the fabric was removed and dried at the same temperature for 5 minutes. A 5 percent solution of magnesium chloride hexahydrate, pH 2.5 was applied with a nebulizer, after which creasing was accomplished at a temperature insufficient for cure. Oven curing was then performed at C, for 5 minutes. After machine washing, and tumble drying, the treated fabric had 0.54 percent bound nitrogen, and a dry and wet wrinkle recovery value of 276and 252(W F) respectively, and the fabric exhibited good flat appearance, and excellent crease retention.

We claim: 1. A process for imparting durable press properties to cotton and other cellulosic fabrics comprising:

a. impregnating the cellulosic fabric with an aqueous solution containing a mixture of formaldehyde and methyl carbamate in molar ratios respectively of from about 2:1

to 4: l said solution adjusted to a H of about 10, b. enclosing the wet impregnate fabric in an airtight package to prevent evaporation,

c. maintaining the wet impregnated fabric in the airtight package to form in situ in the fibers a solution containing about 2.5 to 10 percent of the dimethylol methyl carbamate adduct,

d. removing the fabric from the airtight package to dry the wet impregnated textile for about 3 minutes at about 60 e. applying an acidified magnesium chloride catalyst solution to the impregnated fabric, drying, and

f. curing the dry, impregnated textile for about from 3 to 5 minutes at about 160 C., to yield a cross-linked cellulosic fabric having a durable press properties.

2. The process of claim 1 wherein the fabric is maintained in the airtight package for about 30 minutes at about 60 C.

3. The process of claim 1 wherein the fabric is maintained in the airtight package for about 16 hours at room temperature. 

2. The process of claim 1 wherein the fabric is maintained in the airtight package for about 30 minutes at about 60* C.
 3. The process of claim 1 wherein the fabric is maintained in the airtight package for about 16 hours at room temperature. 